There is an ongoing need to develop compositions and/or methods that are capable of reducing fungus and fungal spores in a plant or crop, and for improving turfgrass and/or grass quality. While many fungicides and compositions are known for controlling various fungi in plants and crops, there is an ongoing demand for new fungicidal compositions. For example, repeated use of fungicides has been known to result in the development of resistant populations of fungus. Furthermore, the fungicidal compositions may be ineffective in controlling the fungus, for example, due to extreme environmental conditions.
Consistent control of Pythium species in plant systems are a wide-scale problem in the industry. Pythium disease, also known as Pythium blight, is a highly destructive turfgrass disease caused by several different Pythium species.
Members of the genus Pythium belong to a group of fungal-like organisms broadly known as water molds. Pythium species belong to the class Oomycota and are commonly referred to as oomycetes. Pythium species are commonly referred to as fungi. However, Pythium species are actually members of the kingdom Chromalveolata.
Pythium aphanidermatum and Pythium ultimum are most commonly associated with Pythium blight. As many as 15 species of Pythium are cited as causative agents of Pythium blight. The most severe symptoms are associated with Pythium aphanidermatum. 
Symptoms associated with Pythium blight are evident during warm, humid weather, specifically when turfgrass remains wet for 12 or more hours. Pythium blight is particularly severe when daytime temperatures exceed 28° C. and night temperatures remain above 20° C.
Initial symptoms of Pythium blight appear as water-soaked leaves that are dark green, blue, brown, or purple in color. Affected leaves aggregate into circular or irregularly shaped patches in turfgrass swards. These patches can range in size from less than 1 cm to greater than 20 cm in diameter.
Infected leaves of turfgrass generally feel slimy or greasy to the touch. Patches of infected grass can enlarge and coalesce, thereby causing damage to lawns, golf courses and athletic field turf. Pythium blight can also manifest in streak patterns in areas in which the disease is spread by flowing water or mowing equipment.
Foliar blight, crown rot, stolon rot, and root rot are associated with Pythium blight.
Pythium blight, also referred to as “spot blight”, “grease spot”, or “cottony blight,” was first reported in the 1930s. Initially, Pythium blight was thought to only affect golf course turf. However, this disease is now recognized as a problem for lawns and athletic fields as well.
Pythium has been detected on warm- and cool-season turfgrass species in the United States, Canada, Germany, France, and Japan.
Fungicides in several classes have been shown to be effective for controlling Pythium. These classes of fungicides include aromatic hydrocarbons, carbamates, dithiocarbamates, phenylamides, phosphonates, and quinone outside inhibitors, which include strobilurins.
The first fungicides used to control Pythium include inorganic mercury, captan, dichlone, cycloheximide, and organic mercury compounds. However, these compounds only exhibited limited control of Pythium blight.
In 1979, the fungicide metalaxyl was registered in the United States for purposes of controlling oomycetes. This included the specific use for controlling Pythium blight on turfgrasses.
Additional fungicides used to control Pythium include mefenoxam (Subdue Maxx®) and propamocarb (Banol®), cyazofamid (Segway®) and fluopicolide (Stellar®), which have been shown to be effective.
However, repeated use of fungicides, particularly metalaxyl or mefenoxam, may select for resistant populations of Pythium aphanidermatum. In 1983, metalaxyl-resistant populations of Pythium aphanidermatum were detected in creeping bentgrass samples taken from Pennsylvania golf courses where metalaxyl was used extensively over a period of three years. More recently, isolates of Pythium ultimum taken from greenhouse-grown ornamental and turfgrass plants have shown resistance to mefenoxam in laboratory assays.
Furthermore, phosphonate products, such as fosetyl A1 (Chipco Signature®), may be effective only when applied as a preventative measure, and only when Pythium blight pressure is low to moderate.
Additional methods of controlling Pythium include sterilization of irrigation equipment, water bodies, plant growing systems based on hydroponics, and sand-based growing media.
There is a continuing need to provide compositions and methods for controlling fungal infestations and Pythium blight in plants, such as turfgrass and other ornamental plants, as well as greenhouse and field crops.